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Full text of "Measurements of the Longitudinal Stability and Control and Stalling Characteristics of a North American P-51H Airplane (AAF No. 4-64164)"

CLASSIFICATION CANCELLED 

naca 






RESEARCH MEMORANDUM 

for the 

Air Materiel Command, U. S. Air Force 

MEASUREMENTS OF THE LONGITUDINAL STABILITY AND CONTROL AND STALLING 
CHARACTERISTICS OF A NORTH AMERICAN ?-51H AIRPLANE 
(AAF NO. h 6kl6k) 
By 

Christopher C. Kraft, Jr., and J. P. Reeder 

Langley Memorial Aeronautical Laboratory 
Langley Field, Va. 



T* cor 



CONTAINS PROPRIETARY 
INFORMATION 



NATIONAL At> 




rGt MBBna BQgB—P 

This document contains classified Into mfij 
tweeting the National Defi 
Stales within the meaning of 

U9C 50:31 and 32. IU tr 
revelation of lla contents In any 
unauthorized perl 
Information so 
only to persOE 

services of the United StatcsflUpj 
civilian officers and employees W 
Government who have a legltlmat 
therein, and to United States citizen 
loyalty and discretion who of neces; 
informed thereof. 



FOR AERONAUTICS 

WASHINGTON 

MAR 2 3 1948 



file copy 

To be r mu' (MO to 
the files' oi m vwk 



m 



CLASSlFlGjVtl^ CONFIDENTIAL a 

l Security Information 



AoV u'v Oom-rotree 
to Aeronautics 

Wasntngton, 0. 



w ~ HT5ecunty Information 

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 



RESEARCH MEMORANDUM 
for the 

A3r Materiel Command, U. S. Air Force 



MEASUREMENTS OF THE LONGITUDINAL STABILITY AND CONTROL AND STALLING 
CHARACTERISTICS OF A NORTH AMERICAN P-51H AIRPLANE 
(AAF NO. k-6kl6k) 
By Christopher C. Kraft, Jr., and J. P. Reeder 

SUMMARY 



Flight tests have been made to determine the longitudinal stability 
and control and stalling characteristics of a North American P— 51H air- 
plane. The results indicate that the airplane has satisfactory longitudi- 
nal stability in all the flight conditions tested at normal loadings up 
to 25,000 feet altitude. At Mach numbers above 0.7, the elevator push 
force required for longitudinal trim decreased somewhat because of com- 
pressibility effects. The elevator stick force per g in accelerated 
turns at the forward center— of -gravity position of 2k percent mean aero- 
dynamic chord above 250 miles per hour was in excess of the required 
limits at both 5,000 and 25,000 feet altitude. The longitudinal-trim- 
force changes due to flaps and power were small, but the rudder— trim- 
force change with power change was high. The stalling characteristics 
in all the conditions tested were satisfactory. 



INTRODUCTION 



At the request of the Air Materiel Command, U. S. Air Force, flight 
tests have been made to determine the flying qualities of a P— 51H airplane 
(AAF No. h-Sklik) . The results of the tests to determine the longitudinal 
stability and control and stalling characteristics are presented herein. 
Data on the lateral and directional stability and control have been 
j presented in reference 1. 

I 

DESCRIPTION OF AIRPLANE AND TESTS 



The P— 51H is a low-wing fighter airplane equipped with a 
Merlin V-I650-9 engine. The configuration used in making the 




ity Information 



2 



CONFIDENTIAL 



NACA RM No. SL8B24 



longitudinal— stability tests was the final production airplane which 
incorporated a 7-inch fin extension, a short-span rudder with the travel 

limited to ±25°> and a ^-inch-chord extension strip added to the entire 

elevator trailing edge with the exception of the elevator tabs. Some 
initial tests were conducted without the elevator trailing-edge extension 
and with the original-vertical— tail configuration. The original vertical 
tail did not have the 7— inch fin extension nor the short— span rudder, 
and the rudder travel was ±30° (reference 1). A three-view drawing of 
the airplane is shown in figure 1 and photographs of the test airplane are 
shown in figures 2 to 5- Other pertinent dimensions of the airplane are 
presented in table I. 

The airplane was tested with three different center— of -gravity 
positions; namely, 2k, 26, and 30 percent of the mean aerodynamic chord. 
All of the center-of -gravity positions given in this paper are with the 
landing gear down. During all the tests, fuel was uBed from the wing 
tanks only. At the two aft center— of -gravity positions, the fuselage 
tanks were filled and used as ballast. The rearward center— of —gravity 
position was obtained by adding 125 pounds of lead to the tail compart- 
ment of the airplane. This center— of— gravity position was aft of any 
normal loading of the airplane but was used to determine the stability 
of the airplane more accurately. The normal center— of— gravity limits 
were approximately 20 to 28 percent of the mean aerodynamic chord. The 
airplane weight varied from 7500 pounds to 9800 pounds during the tests. 

The physical characteristics of the airplane are shown in figures 6 
to 10. The variations of the rudder deflection with rudder— pedal position 
and the elevator and aileron deflection with stick position are shown in 
figures 6 to 8. The friction in these various control systems is shown 
in figure 9. The friction in all of the controls was small and well 
within the required limits specified in reference 2. The stretch in 
each of the controls was measured and is presented in figure 10. These 
data showed the stretch in the aileron control system to be 2.5° P e r 
20 pounds of stick force, the stretch in the elevator control system to 
be 1.2° per 20 pounds of control force, and the stretch in the rudder con- 
trol system to be 7. 5° per 100 pounds of rudder— pedal force. 



The airplane was tested In the following flight conf igurations at 
approximately 5000 feet altitude: 



Condition 


Power 


Flaps 


Gear 


Canopy 


Power-on 


clean 


k6 


inches Kg at 


2700 


rpm 


Up 


Up 


Closed 


Power-off 


clean 


Engine idling 






Up 


Up 


Closed 


Land i ng 




Engine idling 






Down 


Down 


Open 


Approach 




23 


inches Hg at 


2700 


rpm 


Down 


Down 


Open 


Wave-off 






inches Hg at 


2700 


rpm 


Down 


Down 


Open 



CONFIDENTIAL 




NACA RM No. SL8B24 



CONFIDENTIAL 



Tests were also run at high altitude, approximately 25,000 feet, 
in the power— on clean and power— oft' clean conditions. 

All of the tests made were performed "by the steady— record method 
with the exception of the stall-approach data. In the steady— record 
method, records are taken at different speeds or accelerations, as the 
case may he, when the airplane is in a steady condition; whereas in the 
continuous— record method, records are taken continuously as the speed is 
varied slowly over a certain speed range. The continuous records are 
indicated by flagged symbols in this paper. 



INSTRUMENTATION 



Standard NACA photographically recording instruments were used to 
measure the data presented in this paper along with the pilot's readings 
of altitude, free— air temperature, and fuel— gage readings in the cockpit. 
A more complete description of the instrumentation used is presented in 
reference 1. 



DISCUSSION AND RESULTS 



The following discussion of the results obtained from these tests 
is based on the flying— qualities requirements of reference 2. 



Longitudinal Stability and Control 

Dynamic longitudinal stability .- The dynamic longitudinal stability 
of the airplane was tested by trimming the airplane at a given speed and 
in a particular configuration and abruptly deflecting and releasing the 
elevator. Typical time histories of this maneuver are presented in 
figures 11 to Ik. The airplane was tested in all the flight configurations 
and it was found that the oscillation produced by this maneuver was com- 
pletely damped in 1 cycle or less and that there was no oscillation of the 
elevator itself following its deflection. The airplane met the require- 
ments of reference 2 for this particular test. No 'unstable oscillations 
were experienced during any of the tests performed, which were limited to 
Mach numbers below 0.6. 



In flight-testing the first models of the P-^IH airplane at 
Wright Field, several airplanes experienced violent longitudinal 
oscillations, termed "porpoising," at Mach numbers above approximately 0.6 
when the elevator was abruptly deflected. The ^.-'nch trailing-edge strips 
on the elevator were added to cure this deficiency. No short-period- 
oscillation tests were made by the NACA in the Mach number range in which 
porpoising was encountered because of the danger of this maneuver. No 



CONFIDENTIAL 



k 



CONFIDENTIAL 



NACA RM No. SL8B24 



porpoising was experienced, however, in normal flight and dives up to a 
Mach number of 0.75 with the modified airplane. 

Static longitudinal stability .- The static— longitudinal— stability 
data measured in the various configurations are shown in figures 15 to 21. 
These data were obtained by trimming the airplane at a given speed for 
zero control forces and flying the airplane through the speed range from 
the maximum speed obtainable in the various configurations to the stalling 
speed. The requirements state that the curves of elevator force and 
elevator position against airspeed shall have a stable slope at all normal 
center— of -gravity positions; that is, the stick-fixed and stick— free 
neutral points shall be aft of the most rearward center— of— gravity position 
of the airplane. 

The stick— free and stick— fixed neutral points were obtained by the 
method illustrated in figure 22. The elevator force divided by impact 
pressure F e /q and elevator deflection 8 e were plotted against airplane 

normal-force coefficient C M . The slopes of these curves -t#^ and 

dC N dC N 

were then plotted against center— of -gravity position. The center— of— gravity 

dF /q do . 

positions at which ;°' — and — °- are zero are the stick— free and stick— 

dL N dC N 

fixed neutral points, respectively. In cases in which the longitudinal 
stability was large, the actual values of the neutral points obtained 
cannot be considered accurate because they were so far aft of the center— of — 
gravity range tested. They do show, however, the large degree of stability 
that the airplane has. 



(1) Power— on clean condition: The data shown In figures 15 and l6 
indicate the airplane to be stable both stick free and stick fixed, the 
neutral points being aft of the most rearward center— of gravity position. 
The push forces encountered at high speeds with a trim speed of 185 miles 
per hour were practically the limit of the pilot's strength, but had the 
airplane been trimmed at a higher speed, the forces experienced at high 
speed would not have been as high. The effect of altitude on the longitud- 
inal stability was negligible. However, at high speeds and high altitudes 
where higher Mach numbers were obtained, compressibility effects caused 

a tendency for the push force to decrease. (See fig. 16.) 

(2) Powei — off clean condition (figs. 17 and 18): The airplane was 
stable both stick fixed and stick free in this condition at the two forward 
center— of— gravity positions and met the requirements of reference 2. How- 
ever, at the rearward center— of -gravity position tested, a slightly unstable 
elevator— angle variation was noted at high speed. 

(3) Wave-off, approach, and landing conditions (figs. 19 to 21): 

The requirements of reference 1 were met in each of these three conditions. 
The curve 3 of elevator force and angle against speed had a stable slope, 

the stick-free and stick— fixed neutral points being aft of the rearward 

centei — of -gravity position tested. 

CONFIDENTIAL 




NACA RM No. SL8B24 



CONFIDENTIAL 



5 



Longitudinal control .- (1) Longitudinal control in accelerated flight: 
The longitudinal control in accelerated flight was measured by making 
accelerated turns both to the left and right at a constant airspeed and 
acceleration. The tests were made at the three center— of— gravity positions 
at speed3 varying from 200 to 350 miles per hour at approximately 5,000 and 
25,000 feet altitude. Time histories of short records taken in typical 
accelerated turnB are shown in figure 23. The change in elevator force 
and angle obtained from these tests was plotted as a function of change 
in normal acceleration so that the force and angle per g could be determined. 
The elevator angle was also plotted as a function of airplane normal— force 
coefficient in order to obtain the stick— fixed maneuver points. The stick- 
free and stick— fixed maneuver points were determined by measuring the 
average values of the slopes dF e /dg and d6 e /dC N and plotting these 

values as a function of the center— of -gravity position. The center-of- 
gravity positions at which these slopes became zero were the stick— free 
and stick— fixed neutral points, respectively. These data are given in 
figures 2h to 33- A graph of the center-of-grav1 ty range as a function 
of altitude in which desirable values of stick force per g are obtained 
at 300 miles per hour is shown in figure 3*+. 

The force per g with the center— of— gravity position at or forward 
of 27 percent of the mean aerodynamic chord above 250 miles per hour was 
in excess of the required limit of 8 pounds per g specified In the require- 
ments of reference 2. Increasing the altitude from 5,000 to 25,000 feet 
slightly decreased these forces. At the two lower speeds tested, 200 and 
250 miles per hour, the force— per— g characteristics were within the required 
3 to 8 pounds per g limits specified In the requirements. The effect of 
altitude at these two speeds was to decrease the force per g approximately 
1 to 2 pounds. The elevator angle required to produce the acceleration 
was always in the right direction and of a desirable magnitude at all the 
center-of— gravity positions, speeds, and altitudes tested and the elevator 
was always powerful enough to produce the maximum lift coef Picient . 

In general, the force— per-g charac terist 1 cs of the airplane were 
acceptable. The variation of elevator force and angle wa3 linear in all 
the conditions tested, but a3 was mentioned in the preceding paragraph, 
the forces experienced at the higher speeds were slightly grnater than 
the required limits. The most forward stick-free maneuver point obtained 
was at 35 percent of the mean aerodynamic chord at 300 miles per hour mid 
the higher test altitude. The mo3t forward stick— fixed maneuver point was 
found to be at approximately 2k. k percent of the mean aerodynami c chord 
at 350 miles per hour at high altitude, approximately 20,000 feet. The 
stability was greater, however, at all the lower speeds tested where the 
maneuver point is at approximately 27 percent of the mean aerodynamic 
chord at this altitude. 

(2) Longitudinal control in landing and take-off: The airplane met 
the requirements of reference 1 in both landing and take-off. With the 



CONFIDENTIAL 



6 



CONFIDENTIAL 



NACA RM No. SL8B24 



center— of— gravity position In the most forward position it was possible 
to hold the airplane off the ground at approximately 100 miles per hour 
with the airplane trimmed at 120 miles per hour. The elevator force 
required in this procedure did not exceed the 35— pound limit. It was 
also possible during take— off to maintain any attitude up to thrust 
axis level at approximately ^0 miles per hour. These two results were 
determined from pilot's observations. The pilot considered the landing 
and take— off characteristics of the airplane acceptable, except that 
with engine idling the glide path was steep in the landing condition and 
the rate of descent very high. 

(3) Trimming characteristics: It was possible to trim the airplane 
by use of the elevator tabs in all the conditions required according to 
reference 2. The longitudinal trim changes with power, flaps, and gear 
change are shown in table II. The elevator and aileron— trim— force changes 
were no more than 7 pounds, but the pilot objected to the nose-up trim 
change due to flap deflection. The rudder— trim— force change was high 
with change in power. The rudder— trim— force change with change in power, 
power— off to normal rated power, with the airplane trimmed at 135 miles 
per hour was approximately 93 pounds. 

(h) Pitching moment due to sideslip: The pitching moment due to 
sideslip in this airplane was not excessive and was considered satisfac- 
tory. The variation of elevator force with sideslip angle in the power- 
on clean and power— off clean condition is shown in figure 35 for both 
the original and production configurations. The variation of elevator 
angle with sideslip angle is not shown since complete data were not obtained 
for all the conditions. The elevator-angle variation with sideslip was 
found to be small and essentially the same, however, with both tall 
configurations. The differences in the two tails were not of a type 
which would be expected to affect the elevator— angle variation with side- 
slip. 

From the data presented in figure 35> it can be seen that the 
variation of elevator force with sideslip at 300 miles per hour was 
different for the two configurations. The original tail showed very 
little force variation with sideslip over the range of sideslip angles 
measured; whereas the production tail required pull forces as the side- 
slip was increased to the left or right. While this force variation was 
not considered objectionable on the P— 51H airplane, this amount of force 
variation has been considered undesirable on airplanes with a smaller 
amount of longitudinal stability because it resulted in appreciable 
changes in normal acceleration when the rudder was deflected. The 
increased force variation with the traillng-edge extension on the 

elevator probably results from the more negative values of C, and C 

h a. h 6 

of the modified elevator. It was not thought previously, however, that 
this type of modification would have a pronounced effect on the elevator- 
force variation with sideslip. 



CONFIDENTIAL 



NACA RM No. SL8B21+ 



CONFIDENTIAL 



7 



Similar effects, though smaller in magnitude, are shown at 
150 miles per hour in the power— on clean condition. There is very 
little difference between the two tails in the power— off clean condition 
at 150 miles per hour. 



Stalling Characteristics 

In the power— on clean condition (figs. 36 and 37) stall warning 
was afforded by buffeting approximately 5 miles per hour above the stall 
accompanied by mild pitching and rolling in either direction. A pitching 
and rolling oscillation developed near the stall, the airplane finally 
rolling slowly off. The lateral oscillation which occurred at the stall 
could be controlled with moderate difficulty. The stalling characteristics 
were considered etatisfactory . 

Stall warning was supplied by buffeting about 5 miles per hour above 
the stall in the power— off clean condition (figs. 38 and 39) which increased 
as the stall was approached. At the stall, mild pitching and roll to the 
right occurred after which the airplane either spiraled off or developed 
a mild pitching and rolling oscillation. The airplane could be easily 
controlled both laterally and directionally beyond the stall by normal 
use of the controls even to full— up elevator, and recovery from the stall 
vas normal and prompt. The stalling characteristics were considered very 
satisfactory. 

The stall in the wave-off condition (figs, ho and hi) was preceded 
by mild buffeting about 5 miles per hour above the stall. During the 
stall approach the airplane became extremely left wing heavy and required 
considerable right rudder. At the stall a rather abrupt left roll occurred 
which checked itself at about 30° bank as the nose dropped. The airplane 
could not be satisfactorily controlled laterally during the stall. At the 
aft center— of -gravity position with the airplane trimmed at 135 miles per 
hour the stick force reversed and became slightly negative about 7 miles 
per hour above the stall. The stalling characteristics were considered 
acceptable. 

In the approach condition (fig. 42) mild buffeting preceded the stall 
by about 5 miles per hour. Before the stall there was noticeable left 
wing heaviness and after the stall was reached the airplane rolled moder- 
ately to the left to about 30° bank, checked itself and rolled again. The 
airplane could be controlled laterally by the ailerons but there was a 
delay between application of control and recovery response. The stalling 
characteristics were satisfactory. 

In the landing condition (figs, hi and hh) stall warning was afforded 
by buffeting about 2 or 3 miles per hour above the Btall. At the stall 
the nose of the airplane dropped with a mild right roll which resulted in 
pitching the airplane out of the stall. After this recovery the airplane 
sometimes spiraled but more often oscillated in roll and pitch, the pitching 
oscillations increasing, resulting in subsequent stalls being made under 



CONFIDENTIAL 



8 



CONFIDENTIAL 



NACA RM No. SL8B24 



increasing acceleration. Recovery from the stall was normal. The airplane 
could be controlled "both laterally and direct! onally beyond the stall with 
a little difficulty, even with full-up elevator. If the stall was prolonged, 
the airplane would roll off sharply. The stalling characteristics were 
satisfactory. 

The stall in accelerated turns (fig. ^5) was preceded by ample 
buffet warning and, if the stick was continued back, the buffeting became 
very heavy. The stall was accompanied by a slight lateral instability 
which could be easily controlled. At the aft center-of -gravity position 
tested, there was a noticeable control force lightening in both left and 
right turns. The stalling characteristics were satisfactory. 



CONCLUSIONS 



1. The short— period longitudinal oscillations of the airplane were 
stable in all the conditions and speeds tested. The longitudinal oscil- 
lations always damped in 1 cycle or less and there was no oscillation 

of the elevator itself. No short— period— oscillation tests were made at 
Mach numbers above 0.6. however. 

2. The airplane had satisfactory stick-free and stick— fixed static 
longitudinal stability in all the conditions tested and met the handling- 
qualities requirements at altitudes up to approximately 25,000 feet. 
Compressibility effects indicated by decreased push forces were apparent 
at high Mach numbers? in the power— on clean condition. 

3. The longitudinal control in accelerated flight was in general 
satisfactory. However, the force per g with the center-of -gravity 
position at or forward of 27 percent of the mean aerodynamic chord 

above 250 miles per hour was in excess of the required limits. Increasing 
the altitude from 5,000 to 25,000 feet slightly decreased these forces. 
The most forward stick— free maneuver point was 35 percent of the mean 
aerodynamic chord and the most forward stick— fixed maneuver point was 
approximately 27 percent of the mean aerodynamic chord except at high 
speed and high altitude where the maneuver point moved forward to 
approximately 24 percent of the mean aerodynamic chord. 

h. The characteristics of the airplane during take-off and landing 
were satisfactory. 

5- It was possible to trim the airplane longitudinally by use of 
the elevator tabs at all the speeds and in all the conditions required. 

6. The trimming characteristics with change in power and flaps and 
landing— gear position were satisfactory except that the rudder— trim- 
force change due to power was excessive. 

7. The pitching moment due to sideslip was considered satisfactory. 



CONFIDENTIAL 



NACA RM No. SL8B24 



CONFIDENTIAL 



9 



8. The airplane had satisfactory stalling characteristics in all the 
conditions tested. There was ample stall warning in the form of buffeting 
and recovery was always normal and prompt. 



Langley Memorial Aeronautical Laboratory 

National Advisory Committee for Aeronautics 
Langley Field, Va. 



Christopher C. Kraft, Jr. 
Aeronautical Research Scientist 

* T r\ Vi >-i n ^vi 



John P. Reeder 
Aeronautical Research Scientist 



Approved: 

Melvin N. Gough (/ 
Chief of Flight Research Division 



MCF 



REFERENCES 



1. Kraft, Christopher C, Jr., and Reeder, J. P.: Measurements of the 

Lateral and Directional Stability and Control Characteri sties of 
a P-51H Airplane (AAF No. kk-6kl6k) . NACA RM No. L7L11, Army Air 
Forces, 19^7. 

2. Anon.: Stability and Control Characteristics of Airplanes, AAF Speci- 

fication No. R-1815-A, April 1, 19^5- f^dthi^txA 



CONFIDENTIAL 



10 CONFIDENTIAL NACA m N °- SL8B24 

TABLE I 

PERTINENT AIRPLANE DIMENSIONS 

Engine Merlin V-I650-9 

Propeller (4 blades) Aeroproducts Model H-20-156-23M5 

Wing area, sq ft 235.73 

Wing span, ft 37-03 

Aspect ratio 5-82 

Wing-flap area (two), sq ft 31.53 

Aileron area (one), eq ft 6.35 

Total horizontal-tall area, sq ft 48-35 

Elevator area (one), sq ft 6.43 

Original vertical— tail area, sq ft 23.40 

Original rudder area, sq ft 10.24 

Production vertical— tail area, sq ft 24.76 

Production rudder area, sq ft 9-77 

Dorsal— fin area, aq ft 1-93 



CONFIDENTIAL 



TABLE II 

LONGITUDINAL TRIM CKANGES DUE TO FLAPS AND POWER 



Center of gravity at 21.9 percent M.A.C 



(mph) 




Fls.p8 




Control force 
(It) 


Change in 
sideslip 

Mpj 'I 

taeg ; 


Elevator 


Rudder 


Aileron 


151 


* normal rated power 


Up 


Up 














153 


_„__ 


-do- 


Down 


3.0 pull 


1 left 


0.5 right 


0.3 right 




Hn 


Tiri\_rn 
±JyJ w - 1 


- c\ n- 


4.2 push 


2 right 


1.0 right 


u . j r 1 gn t 


1^1 


Off 


-do- 


- d - 


1-3 push 


25 left 


1.0 right 




J-3P 


i normal rated power 


— A r\ — 

U.O 


- j _ — 

Q.O 














1^6 


Off 


-do- 


_ (i _ 





35 left 





1 7 -r' crht 


150 


do 


Up 


Up 














148 


do 


- do- 


Down 


3.0 pull 


4 right 





0.9 right 


149 


- do 


Down 


- do- 


0.5 push 


2 right 


1.0 left 


0.6 right 


135 




-do- 


- do- 














135 


^Normal rated power 


_do- 


- do- 


2.7 push 


93 right 


0.5 right 


1.3 left 


136 


do 


-do~ 


- do- 














135 


do 


- do- 


Up 


0.5 push 











133 


do 


Up 


-do- 


1.0 pull 


20 right 


1.5 left 


1.8 left 


115 




- do- 


Down 














115 




_ do- 


Up 





11 left 





0.2 left 



i normal rated power - 23 in. Hg at 2700 rpm. ^vNAC£- 
Normal rated power — 46 in. Hg at 2 7 00 rpm. 



NACA KM No. SlSB2k 



CONFIDENTIAL 



FIGURE LEGENDS 



Figure 


1.- 


Three— view drawing of the P— 51H airplane with the 
production tail. 


Figure 


2.- 


Side view of North American P— 5-LH airplane. 


Figure 


3.- 


Front view of North American P— 51H airplane. 


Figure 


h.~ 


Three-quarter rear view of North American P— 51H airplane. 


Figure 


5-- 


Three-quarter front view of North American P— 51H airplane. 


TP H cri ] r*p 


6.- 


Vflrl fit, 1 On of* vi in r\ p»t* pi n lt*1 ^ ti ^ i~ Vi t*i irl *-*"k» t\*^H h 1 -nriai f i r\n 

V CLX luUlUil W X X lXl_XkXO X J.-lf. .. ,■ Wl OIX J. LXkXLXOX tJCJLLCLX ^JLJoJ. OlUIij 

P— 51H airplane. 


Figure 


7-- 


Variation of elevator angle with stick position, 
P— 51H airplane. 


Figure 


8.- 


Variation of aileron angle with stick position, 



P— 51H airplane. 



Figure 9.— Variation of the friction force in the control systems with 
elevator, aileron, and rudder angle as measured on the ground in 
the no— load condition, P— 5LH airplane. 

Figure 10.— The variation of stretch in the control systems with 

rudder, elevator, and aileron angle as measured on the ground, 
P— 51H airplane. 

Figure 11.— Time history of a short— period oscillation in the power- 
on clean condition started "by an abrupt deflection and release of 
the elevator. Low altitude, e.g. at 21.15 percent M.A.C., 
P— 51H airplane. 

Figure 12.— Time history of a short— period oscillation in the powar— 
off clean condition started by an abrupt deflection -and release of 
the elevator. Low altitude, e.g. at 21.1+5 percent M.A.C., 
P— 51H airplane. 

Figure 13.— Time history of a short— period oscillation started from an 
abrupt deflection and release of the elevator. High altitude, 
e.g. = 22.77 percent M.A.C., P-51H airplane. 

Figur« Ik .— Time history of a short-period oscillation in the landing 
condition started by an abrupt deflection and release of the 
elevator, e.g. = 23. 60 percent M.A.C., P-51H airplane. 

Figure 15-— Static longitudinal stability characteristics in the power-on 
clean condition at approximately 7000 feet altitude, P— 51H airplane. 

CONFIDENTIAL 



2 



CONFIDENTIAL 



NACA EM No. SL8B2l| 



FIGURE LEGENDS - Continued 



Figure 16.— Static longitudinal stability characteristics in the power— on 
clean condition at approximately 2l+,000 feet altitude, P— 51H airplane. 

Figure 17.— Static longitudinal stability characteristics in the power- 
off clean condition at approximately 7000 feet altitude, 
P— 5-1H airplane . 

Figure 18.— Static longitudinal stability characteristics in the power- 
off clean condition at approximately 22,000 feet altitude, 
P— 51H airplane . 

Figure 19.— Static longitudinal stability characteristics in the wave- 
off condition at approximately 5000 feet altitude, P— 51H airplane. 

Figure 20.— Static longitudinal stability charactertistics in the approach 
condition at approximately 5000 feet altitude, P— 51H airplane. 

Figure 21.— Static longitudinal stability characteristics in the landing 
condition at approximately 5000 feet altitude, P— 51H airplane. 

Figure 22.— Determination of the stick— free and stick— fixed neutral points. 

(a) Variation of elevator angle and F e /q with normal— force 
coefficient for the power-on clean, power— off clean, and landing 
conditions at low altitude. 



Figure 22 Continued. 

(b) Variation of elevator angle and F e /q with normal— force 
coefficient for the wave— off and approach conditions. 

Figure 22.- Continued. 

(c) Variation of ^— £ and with center-of-gravity position 

dC N dC n 

in the power-on clean and power-off clean conditions. 



Figure 22.— Continued. 



(d) Variation of ^S. and fck with center-of— gravity position 
abjy dC^ 

in the wave— off and approach conditions. 



Figure 22.- Concluded. 

(e) Variation of jjj^ and with center-of-gravity position 

in the landing condition. 

CONFIDENTIAL 



NACA RM No. SL8B2l| 



CONFIDENTIAL 



3 



FIGURE LEGENDS - Continued 



Figure 23.— Time histories of accelerated turns in the power— on clean 
condition at approximately 5000 feet altitude. Center-of-gravity 
position at 23. k percent M.A.C., P— 51H airplane. 

Figure 2k,— Variation of the change in elevator force and angle with 
change in normal acceleration at various speeds in turns made in 
the power— on clean condition at the forward center-of— gravity position, 
P— 51H airplane. 

Figure 25.— Variation of the change in elevator force and angle with 
change in normal acceleration at various speeds in turns made in 
the power— on clean condition at the middle center— of— gravity position, 
P— 51H airplane. 

Figure 26.— Variation of the change in elevator force and angle with 
change in normal acceleration at 200 and 300 miles per hour in turns 
made in the power— on clean condition at the aft center— of— gravity 
position, P— 51H airplane. 

Figure 27 .— Variation of the change in elevator force and angle with 
change in normal acceleration in turns at various speeds made in 
the power— on clean condition at high altitude at the forward 
center-of— gravity position, P— 51H airplane. 

Figure 28.— Variation of the change in elevator force and angle with 
change in normal acceleration in turns at various speeds made in the 
power— on clean condition at high altitude at the middle center-of- 
gravity position, P— 51H airplane. 

Figure 29.— Variation of the elevator angle with normal— force coefficient 
in turns at various speeds in the power— on clean condition, 
P— 5LH airplane. 

(a) Forward center-of— gravity position at low altitude. 
Figure 29.— Continued. 

(t>) Middle center— of— gravity position at low altitude. 
Figure 29.— Continued. 

(c) Aft centei^-of— gravity position at low altitude. 
Figure 29.— Continued. 

(d) Forward center-of-gravity position at high altitude. 

CONFIDENTIAL 



k 



CONFIDENTIAL 



NACA RM No. SL8B2U 



FIGURE LEGENDS - Continued 



Figure 29.— Concluded. 

(e) Middle center— of— gravity position at high altitude. 

Figure 30 •— Determination of the stick— free maneuver points at low 

altitude, P— 51H airplane. 

Figure 31.— Determination of the stick— free maneuver points at high 

altitude, P— 51H airplane. 

Figure 32.— Determination of the stick— fixed neutral points at low 

altitude, P— 51H airplane. 

Figure 33 •— Determination of the stick— fixed neutral points at high 

altitude, P— 5LH airplane. 

Figure 3^« — A graph of the center— of— gravity range as a function of 

altitude in which desirable values of stick force per g are obtained 
in turns at 300 miles per hour (average of left and right turns), 
P— 51H airplane . 

Figure 35.— The variation of elevator force with sideslip angle as 
measured in steady sideslips at various speeds in the power— on 
clean and power— off clean conditions at approximately 22,000 feet 
altitude, P— 5LH airplane. 

Figure 36.— Time history of a stall approach in the power-on clean 
condition in which only the elevator was used beyond the stall. 
Center of gravity at 23.6 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 

Figure 37-— Time history of a stall approach in the power-on clean 

condition in which all the controls were used in attempt to control 

the airplane after the stall was reached. Center of gravity at 

23.6 percent M.A.C. at approximately 5000 feet altitude, P— 51H airplan 

Figure 38.- Time history of a stall approach in the power-off clean 
condition in which only the elevator was used beyond the stall. 
Center-of— gravity position at 22.7 percent M.A.C. at approximately 
5000 feet altitude, P-51B airplane. 

Figure y-J.— Time history of a stall approach in the power-off clean 
condition in which all the controls were used in an attempt to 
control the airplane after the stall was reached. Center— of gravity 
position at 22.7 percent M.A.C. at approximately 5000 feet altitude, 
P-51H airplane. 



CONFIDENTIAL 



NACA RM No. SL8B21+ 



CONFIDENTIAL 



5 



FIGURE LEGENDS - Concluded 



Figure UO.— Time history of a stall approach in the wave— off con- 
dition in which only the elevator was used "beyond the stall. 
Center— of -gravity position at 23. h percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 

Figure hi.— Time history of a stall approach in the wave— off condition 
in which all the controls were used in an attempt to control the 
airplane after the stall was reached. Center— of— gravity position 
at 23 . h percent M.A.C. at approximately 5000 feet altitude, 
P-51H airplane. 

Figure .1+2.— Time histories of stall approaches in the approach conditii 
Center-of— gravity position at 23. 1 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 

Figure k$,— Time history of a stall approach in the landing condition 
in which only the elevator was used "beyond the stall. Center— of— 
gravity position at 21.9 percent M.A.C. at approximately 5000 feet 
altitude, P— 51H airplane. 

Figure kk.— Time history of a stall approach in the landing condition 
in which all the controls were used in attempt to control the 
airplane after the stall was reached. Center— of— gravity position 
at 21.9 percent M.A.C. at approximately 5000 feet altitude, 
P— 5LH airplane . 

Figure U5.— Time history of an accelerated stall approach in the 
power— on clean condition in a left turn. Center of gravity at 
30 percent M.A.C. at approximately 65OO feet altitude, 
P— 5LH airplane. 



CONFIDENTIAL 



NACA RM No. SL8B24 





444.3/" 




CONFIDENTIAL 



Figure 1.- Three-view drawing of the P-51H airplane with the 

production tail. 



CONFIDENTI AL 




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Figure 3.- Front view of North American P-51H airplane. 



CONFIDENTIAL 



NACA 



CONFIDENTIAL 





Figure 6.- 



Variation of rudder angle with rudder pedal position, 
P-51H airplane. 



NACA RM No. SL8B24 



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Figure 7.- Variation of elevator angle with stick position, 

P-51H airplane. 



NACA RM No. SL8B24 




Figure 8.- Variation of aileron angle with stick position, 

P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 



Figure 9.- Variation of the friction force in the control systems with 
elevator, aileron, and rudder angle as measured on the ground in 
the no-load condition, P-51H airplane. 



NACA RM No. SL8B24 













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Figure 10.- The variation of stretch in the control systems with 
rudder, elevator, and aileron angle as measured on the ground, 
P-51H airplane. 



NACA RM No. SL8B24 




Figure 11.- Time history of a short-period oscillation in the power- 
on clean condition started by an abrupt deflection and release of 
the elevator. Low altitude, e.g. at 21.15 percent M.A.C., 
P-51H airplane. 



NACA RM No. SL8B24 




Figure 12.- Time history of a short-period oscillation in the power- 
off clean condition started by an abrupt deflection and release of 
the elevator. Low altitude, e.g. at 21.45 percent M.A.C., 
P-51H airplane. 



• 



NACA RM No. SL8B24 




(a) Power-off clean condition, (b) Power -on clean condition, 
e.g. = 22.77. e.g. = 22.77. 

Figure 13.- Time history of a short -period oscillation started from an 
abrupt deflection and release of the elevator. High altitude, 
e.g. = 22.77 percent M.A.C., P-51H airplane. 



NACA RM No. SL8B24 




Figure 14.- Time history of a short -period oscillation in the landing 
condition started by an abrupt deflection and release of the 
elevator, e.g. = 23.60 percent M.A.C., P-51H airplane. 




Figure 15.- Static longitudinal stability characteristics in the power -on 
clean condition at approximately 7000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




gure 16.- Static longitudinal stability characteristics in the power-on 
clean condition at approximately k!4,000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




Figure 17.- Static longitudinal stability characteristics in the power,- 
off clean condition at approximately 7000 feet altitude, 
P-51H airplane. 



NACA RM No. SL8B24 




Figure 18.- Static longitudinal stability characteristics in the power- 
off clean condition at approximately 22,000 feet altitude, 
P-51H airplane. • * 



NACA RM No. SL8B24 




CiZtfJlA-zfa? '111 
CONFIDENTIAL 



gure 
off 



19.- Static longitudinal stability characteristics in the wave- 
condition at approximately 5000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 



Figure 20.- Static longitudinal stability characteristics in the approach 
condition at approximately 5000 feet altitude, P-51H airplane. « 



NACA RM No. SL8B24 




Figure 21.- Static longitudinal stability characteristics in the landing 
condition at approximately 5000 feet altitude, P-51H airplane. 




(a) Variation of elevator angle and F e /q with normal -force coefficient for the power -on 
clean, power-off clean, and landing conditions at low altitude. 

Figure 22.- Determination of the stick -free and stick -fixed neutral points. 




(b) Variation of elevator angle and F e /q with normal -force coefficient for the wave-off 

and approach conditions. 



Figure 22.- Continued 



NACA KM No. SL8B24 




CONFIDENTIAL 



NACA 



d5 P dF e /q 
(c) Variation of ■ and — with center-of -gravity 

dC N dC N 
position in the power -on clean and power-off clean 
conditions. 

Figure 22.- Continued. 



NACA RM No. SL8B24 




CONFIDENTIAL 



(d) Variation of 



dC, 



and 



dF e /q 
dC, 



with center -of -gravity 



'N 

position- in the wave-off and approach conditions. 



Figure 22.- Continued. 



NACA RM No. SL8B24 




dO p clF e /q 
(e) Variation of - — — and with center -of -gravity 

dC N dC N 
position in the landing condition. 

Figure 22.- Concluded. 



NACA RM No. SL8B24 




(a) Left turn. 



(b) Right turn. 



Figure 23.- Time histories of accelerated turns in the power-on 
clean condition at approximately 5000 feet altitude. Center -of - 
gravity position at 23.4 percent M.A.C., P-51H airplane. 



NACA RM No. 



SL8B24 




Figure 24.- Variation of the change in elevator force and angle 
with change in normal acceleration at various speeds in turns 
made in the power -on clean condition at the forward center - 
of -gravity position, P-51H airplane. 



NACA RM No. SL8B24 



in 



mm 



CONFIDENTIAL 




CONFIDENTIAL 




Figure 25.- Variation of the change in elevator force and angle 
with change in normal acceleration at various speeds in turns 
made in the power-on clean condition at the middle center-of- 
gravity position, P-51H airplane. 



NACA RM No. SL8B24 




Figure 26.- Variation of the change in elevator force and angle 
with change in normal acceleration at 200 and 300 miles per 
hour in turns made in the power -on clean condition at the 
aft center-of -gravity position, P-51H airplane. 



JACA KM No. SL 




Figure 27.- Variation of the change in elevator force and angle with 
change in normal acceleration in turns at various speeds made 
in the power-on clean condition at high altitude at the forward 
center -of -gravity position, P-51H airplane. 



NACA RM No. SL8B24 




Figure 28. - Variation of the change in elevator force and angle with 
change in normal acceleration in turns at various speeds made in 
the power -on clean condition at high altitude at the middle center - 
of -gravity position, P-51H airplane. 



NACA RM No. SL8B24 




(a) Forward center -of -gravity position at low altitude. 



Figure 29.- Variation of the elevator angle with normal -force 
coefficient in turns at various speeds in the power -on clean 
condition, P-51H airplane. 



NACA 



RM No. SL8B24 



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(b) Middle center-of -gravity position at low altitude. 
Figure 29.- Continued. 



NACA RM No. SL8B24 





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(c) Aft center-of -gravity position at low altitude. 
Figure 29.- Continued. 



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NACA RM No. SL8B24 



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(d) Forward center-of -gravity position at high altitude. 

Figure 29.- Continued. 



NACA KM No. SL8B24 




(e) Middle center-of -gravity position at high altitude. 
Figure 29. - Concluded. 



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NACA RM No. SL8B24 

























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Figure 30.- Determination of the stick -free maneuver points at low 

altitude, P-51H airplane. 



NACA RM No. SL8B24 




Figure 31.- Determination of the stick -free maneuver points at high 

altitude, P-51H airplane. 



NACA RM No. SL8B24 




Figure 32.- Determination of the stick -fixed neutral points at low 

altitude, P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 



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CONFIDENTIAL 

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Figure 33.- Determination of the stick -fixed neutral points at high 

altitude, P-51H airplane. 




Figure 34.- A graph of the center-of-gravity range as a function of 
altitude in which desirable values of stick force per g are 
obtained in turns at 300 miles per hour (average of left and 
right turns), P-51H airplane. 



NACA RM No. SL8B24 




Figure 35.- The variation of elevator force with sideslip angle as 
measured in steady sideslips at various speeds in the power -on 
clean and power -off clean conditions at approximately 22,000 feet 
altitude, P-51H airplane. 



NACA RM No. SL8B24 



.CONFIDENTIAL 




Figure 36.- Time history of a stall approach in the power-on clean 
condition in which only the elevator was used beyond the stall. 
Center of gravity at 23.6 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




Figure 37.- Time history of a stall approach in the power-on clean 
condition in which all the controls were used in attempt to control 
the airplane after the stall was reached. Center of gravity at 
23.6 percent M.A.C. at approximately 5000 feet altitude, 
P-51H airplane. 



NACA KM No. SL8B24 




Figure 38.- Time history of a stall approach in the power-off clean 
condition in which only the elevator was used beyond the stall. 
Center -of -gravity position at 22.7 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




Figure 39.- Time history of a stall approach in the power-off clean 
condition in which all the controls were used in an attempt to 
control the airplane after the stall was reached. Center-of-gravity 
position at 22.7 percent M.A.C. at approximately 5000 feet 
altitude, P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 

Figure 40.- Time history of a stall approach in the wave-off con- 
dition in which only the elevator was used beyond the stall. 
Center-of -gravity position at 23.4 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 



Figure 41.- Time history of a stall approach in the wave-off condition 
in which all the controls were used in an attempt to control the 
airplane after the stall was reached. Center -of -gravity position 
at 23.4 percent M.A.C. at approximately 5000 feet altitude, 
P-51H airplane. 




(a) Only the elevator was 
used beyond the stall. 



(b) All the controls were used 
in an attempt to control the 
airplane after the stall was 
reached. 




Figure 42.- Time histories of stall approaches in the approach condition. 
Center -of -gravity position at 23.1 percent M.A.C. at approximately 
5000 feet altitude, P-51H airplane. 



NACA RM No. SL8B24 




CONFIDENTIAL 



Figure 43.- Time history of a stall approach in the landing condition 
in which only the elevator was used beyond the stall. Center-of- 
gravity position at 21.9 percent M.A.C. at approximately 5000 feet 
altitude, P-51H airplane. 




Figure 44.- Time history of a stall approach in the landing condition 
in which all the controls were used in attempt to control the 
airplane after the stall was reached. Center -of -gravity position 
at 21.9 percent M.A.C. at approximately 5000 feet altitude, 
P-51H airplane. 



NACA RM No. SL8B24 




Figure 45.- Time history of an accelerated stall approach in the 
power -on clean condition in a left turn. Center of gravity at 
30 percent M.A.C. at approximately 6500 feet altitude, 
P-51H airplane.